Talk:BETA/@comment-5806305-20150625114310/@comment-4391208-20150625124503
You only can't pour salt water on a tree because it goes to the roots, which then take in the water and the salt, resulting in plant damage. The water doesn't enter via the bark if there are no visible wounds on the surface (eg. man-made chipping; dry-weather cracking; budding leaves on branches). Most of the data I can find points to either using salt leaching into nearby soil, or directly inducing salt water into stumps of already-removed trees. For trees with otherwise healthy bark to be vulnerable to salt spray means that they would probably die from dehydration or excess water intake long before the salt could kill them. As you have probably already noticed most land trees avoid shorelines, but that is because wind carries salt-laced water vapours and water sprays inland for a distance, which then leaches into the roots and increases its salinity, making it difficult for non-adapted plant life to survive the increased salt levels of the soil in such areas. The BETA don't cross oceans because they'd run out of power long before they make it halfway there. Deep pressure slows down their movement momentum, extreme pressure would crush them, and they're unable to swim, meaning that they are subject to seafloor geography (valleys, chasms, features that would delay travel time). Being animal-type constructs, if they could be weakened by salt water to a reasonable amount, the effects would have to be extremely fast, fast enough that invasions from the Korean Peninsula, via the Sea of Okhotsk, the English Channel and/or Hokkaido by way of Sakhalin Island would have weakened them enough that the forces present at the area need not constantly carry out land-based culling operations every time there is a force buildup. The power loss from being away from a reactor for too long would end them before any salt damage; any kind of environmental damage that salt corrosion could do to them would take weeks, at least, if not months; essentially a non-consideration in warfare situations. Basically, they simply lack the operating range to travel that distance underwater, and since their operations are considerably slowed underwater, they perhaps avoid setting up operations underwater (in addition to human monitoring and active culling efforts, thus preventing the appearance of an aquatic Hive in Alternative, as of 2001). Although, the water-based planet idea is worth considering. If the planet held no species that overcame its environmental limitations and achieved a level of sentience comparable to humanity during our ascension to civilization (creation and/or control of heat, as well as a tool-based civilization due to reduced effectiveness of kinetic effects in a denser medium then air, as examples) then they could very well take their own sweet time taking over the planet (eg. no sentient species to actively contest them), or perhaps even evolved water-adapted species to speed up their rate of work (eg. Laser-class with more focused beams, Gate-class becoming more widespread, BETA using underground tunnels to move around instead of surface searching). Then again, it could also be that the BETA that entered the Solar System were not from the "branch fleet" that adapted to water environments, or the group that entered a water environ and successfully adapted to it also met a species that has successfully fought it off or still held it in check as of 2001 in Muv-Luv (eg. through active selection of evolutionary traits, like the many swarm-type enemies in science fiction). Evolution seems to be controlled by the Superior rather than as a natural reaction. Perhaps they did not find a need to evolve on an uncontested water-based planet; after the re-purposing of Laser-class for anti-air, it took Earth's Superior almost three decades to create a dedicated countermeasure to human forces (TE's superBETA) after what must have been the destruction of trillions of creatures over the period that humanity had spent waging war.